Signs of Infection After Surgery

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Common signs of a surgical infection include fever, pain, swelling, and a pus-like discharge. Depending on the type of surgery you had, the infection may not only affect the skin where the incision was made, but your muscles and internal organs.

If a surgical infection is severe and not treated appropriately, it can spread into the bloodstream, causing septicemia (blood poisoning) and septic shock (a related, life-threatening drop in blood pressure).

This article explains the types, symptoms, and causes of surgical site infections, as well as how they are prevented and when it is time to see a healthcare provider.

Post-Surgery Signs of Infection

Verywell / Joshua Seong

Types of Infections After Surgery

A surgical site infection (SSI) occurs when an incision and/or underlying tissue is contaminated with bacteria.

There are three types of SSIs:

  • Superficial incisional SSIs: Limited to the incision area
  • Deep incisional SSIs: Develop under the incision, affecting muscles and surrounding tissues
  • Open or space SSIs: Develop in other parts of the body, including organs and the space between organs

The type of SSI you can get is largely influenced by the surgery you have. A superficial incisional SSI, for example, may occur with procedures like mole removal. Open surgeries, such as open-heart surgery, place you at greater risk of an open or space SSI.

Symptoms of Surgical Site Infections

All SSIs are characterized by the following symptoms:

  • Redness, swelling, and warmth: Inflammation is the body's natural response to infection. Inflammation causes blood vessels to swell and fluids to leak into surrounding tissues, causing swelling, warmth, and redness.
  • Pain and tenderness: As a part of the body's immune response, inflammatory chemicals called cytokines are released into the bloodstream that activate pain receptors in the skin and tissues. Pain is one of the ways your body tells you something is wrong.
  • Fever and chills: Fever helps your body kills foreign invaders by increasing the overall body temperature. In the process of resetting your body's thermostat, your body will respond with shivering chills.
  • Pus discharge: White blood cells are tasked with killing bacteria. As your body fights an infection, dead white blood cells start to pile up and mix with dead bacteria and tissue debris to form pus. Pus is thick, foul-smelling, and whitish, yellowish, or slightly greenish in color.

Generally speaking, the symptoms of an open or space SSI are more significant than those of a deep incisional SSI. The symptoms of a deep SSI tend to be worse than with a superficial incisional SSI.

Even so, all three conditions can progress if not treated correctly. If some cases, the infection can spread into the bloodstream, causing a severe systemic (whole-body) infection.

Symptoms by SSI Type

Additional symptoms of an SSI can differ based on the type of SSI you have:

  • Superficial incisional SSIs: These infections may produce pus from the immediate wound site. There may also be a discharge of clear fluid (exudate) from surrounding swollen tissues.
  • Deep incisional SSIs: These infections may also produce pus. The wound site may also reopen (called dehiscence) or get harder as a result of the inflammatory response (called induration).
  • Organ or space SSI: These infections can cause the discharge of pus from a surgical drain. The discharge tends to be smellier and may be mixed with blood. This is because pockets of pus, called abscesses, can form on infected organs and tissues and burst.


If not properly treated, an infection after surgery can spread into the bloodstream and cause a systemic infection called septicemia.

Symptoms of septicemia include:

  • Fever
  • Loss of appetite
  • Fatigue and weakness
  • Nausea or vomiting
  • Rapid heart rate
  • Feeling cold
  • Generalized pain, achiness, or discomfort
  • Light sensitivity

If not treated immediately, septicemia can trigger the overreaction of the immune system, leading to a potentially life-threatening condition known as sepsis.

Sepsis is a medical emergency that can lead to shock, coma, or death if left untreated.

When to Call a Healthcare Provider

Call your healthcare provider immediately if you develop a fever, pus, or pain, redness, swelling, and heat on or around the surgical incision.

Causes of Surgical Site Infections

Surgical site infections are caused by the infiltration of bacteria into the wound and underlying tissues. The most common of these are called StaphylococcusStreptococcus, and Pseudomonas.

Contamination of surgical wounds can happen:

  • During surgery if a surgical instrument is not sterilized
  • After surgery if the wound comes in contact with unclean hands or objects

The risk of an post-surgery infection varies by the classification of the surgical wound:

  • Clean wounds: Those that do not involve surgery on an internal organ and have no evidence of infection or inflammation
  • Clean-contaminated wounds: Involve surgery on an internal organ, but have no evidence of infection or inflammation
  • Contaminated wounds: Surgery on an internal organ causes fluids to spill into the wound and surrounding tissues
  • Dirty wounds: Surgery on an infected internal organ causes fluids to spill into the wound and surrounding tissues

Risk Factors for SSIs

An infection after surgery can happen to anyone, but it is more likely when a procedure:

  • Lasts more than two hours
  • Is emergency surgery
  • Is an abdominal surgery

People at increased risk of infection for different reasons are also at higher risk for infection after surgery. Some of the most common risk factors include:

Prevention of Surgical Infections

There are things you can do to significantly reduce your risk of surgical site infections before and after surgery.

Among the tips:

  • Stop smoking several days before the surgery (and ideally until the wound fully heals).
  • Avoid shaving the skin on or around the planned incision site. Let the nurses do it when you arrive for surgery.
  • After surgery, follow your surgeon's wound care instructions, including when you can bathe and how often you need to change dressings.
  • Asked loved ones not to touch your wound or surgical site.
  • Inspect the wound daily and report any changes to your healthcare provider.
  • Never remove stitches on your own.

You can also ask your surgeon for advice based on the type of surgery you are undergoing.


A postoperative infection, also referred to as surgical site infection (SSI), is a potentially serious complication of surgery. Symptoms include increasing pain, swelling, redness, and heat at the incision site along with fever, chills, and a pus-like discharge.

If left untreated, the infection can spread into the bloodstream and causes sepsis and septic shock. Improper wound care is a common cause of SSIs. People who are older, immunocompromised, smoke, or have uncontrolled diabetes or obesity are at greater risk.

1 Source
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Johns Hopkins Health. Surgical site infections.

Additional Reading

By Jennifer Whitlock, RN, MSN, FN
Jennifer Whitlock, RN, MSN, FNP-C, is a board-certified family nurse practitioner. She has experience in primary care and hospital medicine.